title: Acquired resistance to temsirolimus in human renal cell carcinoma cells is mediated by the constitutive activation of signal transduction pathways through mTORC2.
abstract: BACKGROUND
  The objective of this study was to characterise the mechanism underlying acquired resistance to temsirolimus, an inhibitor of mammalian target of rapamycin (mTOR), in renal cell carcinoma (RCC).
  
  
  METHODS
  A parental human RCC cell line, ACHN (ACHN/P), was continuously exposed to increasing doses of up to 20 μM of temsirolimus, and a cell line resistant to temsirolimus (ACHN/R), showing a sixfold higher IC50 than that of ACHN/P, was developed.
  
  
  RESULTS
  Following treatment with temsirolimus, phosphorylation of S6 kinase in ACHN/P was markedly inhibited, whereas there was no detectable expression of phosphorylated S6 in ACHN/R before and after temsirolimus treatment. However, AKT and p44/42 mitogen-activated protein kinase (MAPK) were constitutively phosphorylated even after temsirolimus treatment in ACHN/R, but not in ACHN/P. There was no significant difference between the sensitivities of ACHN/P and ACHN/R to KU0063794, a dual inhibitor of mTOR complex 1 (mTORC1) and mTORC2. Similar sensitivities to temsirolimus in ACHN/P and ACHN/R could be achieved by additional treatment with specific inhibitors of AKT- and MAPK-signaling pathways.
  
  
  CONCLUSIONS
  The activation of signal transduction pathways via mTORC2, but not via mTORC1, may have an important role in the acquisition of a resistant phenotype to temsirolimus in RCC.
authors.affiliation: Division of Urology, Kobe University Graduate School of Medicine, Chuo-ku, Kobe 650-0017, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Harada
authors.forename: H
authors.initials: H
authors.lastname: Miyake
authors.forename: M
authors.initials: M
authors.lastname: Kumano
authors.forename: M
authors.initials: M
authors.lastname: Fujisawa
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002070:Butadienes / Q000494:pharmacology; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D002070:Butadienes; D002867:Chromones; D009025:Morpholines; D046912:Multiprotein Complexes; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C401859:temsirolimus; C541932:Ku 0063794; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D020123:Sirolimus